Method and apparatus for deep drawing metal



y 5, 1970 J. L; MASSINGILL ETAL METHOD AND APPARATUS FOR DEEP DRAWINGMETAL Original Filed April 23, 1964 8 Sheets-Sheet l 8 Sheets-Sheet 2 y1970 J. MASSINGILL ETAL METHOD AND APPARATUS FOR DEEP DRAWING METALOriginal Filed April 23, 1964 JESS L. MASS/NG/LL I! ALD C. GR/ RENKO G5"May 5, 1970 J. MASSINGILL E 3,509,754

- METHOD AND APPARATUS FOR DEEP DRAWING METAL Original Filed April 23,1964 8 Sheets-Sheet 5 INVENTORS JESS L. MASS/NG/LL DONAL D C. GR/GORENKOB@W/HJ Q22 MWJ -IHI I111.

ATTORNEYS May 5, 1970 ,1. L. MASSINGILL ETAL 3,509,754

METHOD AND APPARATUS FOR DEEP DRAWING METAL Original Filed April 23,1964 8 Sheets-Sheet L INVENTORS m m 0 O LKMN mm A 6 Wm@ sum AG M M L d 0May 5, 1970 J. L. MASSINGILL ET 3,509,754

METHOD AND APPARATUS FOR DEEP DRAWING METAL Original Filed April 2 19648 Sheets-Sheet 5 5 J rd? r415 I 2000 "uh-:5" 01 "7 moo T M6 mq finullnull PM 500 INVENTORS JESS L, MASS/NG/LL ll L0 C. G/Q/GO/PENKO ATTORNEYSJ. L. MASSlNGiLL ET AL 3,509,754

METHOD AND APPARATUS FOR DEEP DRAWING METAL Original Filed April 23,1964 May 5, 1970 8 Sheets-Sheet 6 INVENTORS LO. m MM m 6 WW m mg m LC sw 1970 J. 1.. MASSINGILL mm. 3,509,754

METHOD AND APPARATUS FOR DEEP DRAWING METAL Original Filed April 23,1964 8 Sheets-Sheet '7 a a 4 2 4 4 a S awn 2 1 aw 4 m mLO a a M w a WW4M M 4, a 6 m G N 1 k 7. 5 4 N E 6 l S 7 4 O 7 II V a 6 (V O, S G 3 (M65 Z 7 4 6 a A Z 3 7 4 DH 4 6 M 2 j 2 6 2 n a f G M 4 .m 7 In a a g 2 .ai u 7 a C 2 a m 7 7 7w u u 3 3 a 4 7 a Z lv w/ 7 m G a E. m I 1 1| y w amm "a F w m A JM 3 M M r I 6/ d. 7 8 3 1 7 M 0 a0 7 5 7 W I 5 m m 9 a a/m 2/ a A 4 8 a a M 071 2 7 4/ l M m7 Z: 3; 2 m i 1 w 3 M W 8 M7 a 4 a a9 a F a a 2 2 m 9 K o 7 a 9 0 3 Y W a d 3 0/ 8 w 6 Z s m 2 am J E m a umI M V 1 W a 7 w m r 4 l 5 7 H 3 m H M 9 w I W m: V ,2 4 g E m 1 Q 5 a inPU- h i I l I fl w 1 F m E B w E a m m .L M 6 4 7 M W A 3 ATTORNEYS y1970 J. L. MASSINGILL ETAL 3,509,754

METHOD AND APPARATUS FOR DEEP DRAWING METAL Original Filed April 23,1964 8 Sheets-Sheet 8 JESS L. MASS/NG/LL ALD CGR l GORENKO dimm/ATTORNEYS United States Patent O 3,509,754 METHOD AND APPARATUS FOR DEEPDRAWING METAL Jess L. Massingill, Cape Coral, Fla., and Donald C.Grigorenko, Columbus, Ohio, assignors to Metal Flo Corporation,Columbus, Ohio, a corporation of Michigan Continuation of applicationSer. No. 362,004, Apr. 23,

1964. This application May 28, 1969, Ser. No. 843,882 Int. Cl. B21d22/28 US. Cl. 72-349 32 Claims ABSTRACT OF THE DISCLOSURE CROSSREFERENCE This application is a continuation of our application Ser. No.362,004, filed Apr. 23, 1964, now abandoned.

BACKGROUND OF THE INVENTION The present invention relates to the art ofdrawing metal and provides ways and means for the economical productionof ultra deep drawn metal cans, shells, tubes, and the like, from firstoperation cup shells, fiat blanks, fiat sheet metal strips, and thelike.

In the patented art is found many proposals for effecting the deepdrawing of metal wherein the metal being drawn is subjected to asequence of drawing operations during a single and continuous stroke ofthe drawing apparatus. US. Pat. Nos. 783,390; 961,131 and 1,720,375,granted in 1905, 1910 and 1929, respectively, are typical of suchproposals.

Notwithstanding the numerous patented proposals for the deep drawing ofmetal by a sequence of operations performed during a single stroke ofboth mechanical and hydraulic drawing apparatus, such proposals have notexperienced any general acceptance in this art. No present commercialuse of the many proposals of the above-mentioned type, which appear inthe patented art, is known, nor do such proposals appear in engineeringhandbooks dealing extensively with the art of metal drawing.

A practical commercial process and apparatus for carrying out theprocess according to the present invention has been provided byperforming the drawing operation in a horizontally disposed press inwhich all the major structural and functional components are supported,adjusted and operated on a rigid, horizontally disposed supportstructure on which the weight of such components is distributed, as wellas shifted, during the cycle of operation of the press.

The rigidity of the press of the present invention is augmented by thetelescoping association of the punches which, in addition to forming themetal in the dies, have the further function of serving as pressure padsand pilots during the sequence of the drawing operations. Each punch ofeach operation of the press is rigidly associated with a vertical platewhich is rigidly supported and guided for horizontal movement. As thedrawing operations progress, these plates are moved longitudinally inthe press and sequentially approach one another to effect a substantialshifting of the structural and functional mass 3,509,754 Patented May 5,1970 of the press adjacent the area in which the metal shaping is takingplace.

To maintain a high degree of rigid parallelism between the punchcarrying plates, each plate is carried on a common guide rod system, andthe plates are spaced from each other by several systems of spacerelements which are disposed about each punch. The ram pressure of thepress is transferred from one punch plate to the next through the spacerelements, whereby the operating pressure of the ram and the reaction ofthe metal to shaping both tend to effect parallelism between the punchplates.

The draw dies of the press of the present invention are supported andmaintained in rigid parallelism and concentricity with the telescopingpunches. In each die of each drawing operation, with the exception ofthe first, the metal being formed is transferred from the previousdrawing operation on the punch that performed the previous draw withthat particular punch thereafter functioning as a combination pressurepad and pilot for the drawing operation performed by the followingpunch. Piloting of the Work blank from one punch to the next in eachredrawing die tends to promote and maintain a state of concentricassociation between the dies and punches which contributes to thegeneral rigidity, horizontal alignment and parallelism of the punch anddie carrying components of the press.

To prevent as well as to control relative movement between adjacentpunch carrying plates, hydraulic means are provided which have a lockedstate to prevent relative movement, as well as a regulated state forinitiating the sequential drawing movement of the punches. The hydraulicmeans also provides holding pressure for the metal being shaped as Wellas holding the plates of the moving plate system together.

Through the horizontal arrangement of the press, the ram of the press issubstantially relieved of the dead weight of the punch carrying plates,punches and spacer elements, as well as the components of the hydraulicsystems associated therewith. At the same time the horizontalarrangement of the press facilitates set-up operations, inspections ofthe various operating stages, lubrication of the punches and dies, andcooling of the metal-forming components. It also facilitates the feedingof the stock to the machine and removing of fabricated articles. Anytendency for the horizontal disposition of the punches to causeobjectionable drooping with a resulting lack of concentricity of thepunches in the draw dies has been avoided by the rigid and telescopingassociation of the punches, coupled with a departure in acceptedpractice in metal drawing which provides a high degree of punch huggingby the metal being shaped by a reduction in standard punch and dieclearances to a point approaching an interference fit" with the gauge ofmetal being drawn.

One possible explanation for the unexpected percentage of reduction thatmay be performed by the present invention in a single stroke of thepress, without metal rupture or intermediate anneals, may be contributedto the combination of punch hugging, interference fit" and the pilotingaction of the punches during the transfer of formed metal from one punchto the next in the draw dies. These functions appear to so uniformlydistribute, form and control the metal that stresses on the metal areuniformly distributed with the substantial elimination of localizedareas that are less prepared for redrawing than the remaining portionsof the formed metal.

When the principles of design discussed in the preceding paragraph areemployed in combination with the sequence of drawing operations rigidlyperformed during a single cycle of operation of the drawing press, thegeneration of heat and the substantial continuous flowing of the metalthroughout the cycle obviously contributes to a substantial extent tothe obtaining of greater reductions in blank diameter. However, in orderto ob tain the repetitive results of the present invention more isrequired than merely sequential drawing operations performed during asingle and continuous stroke of the press.

Thus, an object of the invention is to provide an improved drawing pressfor the deep drawing of metal articles wherein a sequence of drawingoperations is performed without intermediate annealing through novel andcoordinated control of punch movement, through the regulation of therestraining pressures on the metal blank at each drawing operation, andthe character of the association of the metal blank with the punch anddie structure of each drawing operation.

Another object of the invention is to provide an improved press for thedeep drawing of metal articles without annealing wherein rupture of theclosed end of the metal blank being drawn is avoided through novelassociation of the metal blank with the punch and die structures whichperform the drawing operations.

A further object is to provide an improved press for the deep drawing ofmetal articles without annealing wherein the stresses of the drawingoperation are uniformly distributed throughout the circumference of themetal blank to permit substantial increases in the percentage ofreduction of metal blanks during the drawing operation as compared withstandard practices and without experiencing metal rupture.

Still a further object of the invention is to improve the art of deepdrawing of metal articles through improved means for the presentationand transfer of the metal blank with respect to the operation carriedout in the drawing die.

Another object of the invention is to provide a novel drawing press inwhich the ram of the press is preterably horizontally disposed and thepunch structure is supported and moved along a horizontally supported,vertically disposed structure with concentricity and alignment of thepunch structure being provided by a novel arrangement of telescopingpunches and punch carriers.

A still further object is to provide a novel press for performing asequence of drawing operations during a single stroke of the press inwhich movement of the ram is transferred to the metal blank through aseries of independently supported and independently guided punchcarriers, the carriers having common guide and common support structuresas well as telescoping and nested association for augmenting parallelismof the punch carriers on their common support structure.

A still further object of the invention is to provide a deep drawingpress having a series of punch carriers which are independentlysupported and relatively movable, the carriers being spaced for bothunitary and relative movement, with respect to each other, by the ram ofthe press through the control of fluid cushions.

A further object of the invention is to provide a press of the designdescribed in the preceding paragraph wherein the fluid cushion structurealso functions to control the pressure on the metal blank during eachdrawing operation.

Another object is to provide a hydraulic deep drawing press in whichnovel coordination of hydraulic means is provided for controlling punchand pressure pad means during the sequential operation of the metaldrawing structure.

BRIEF DESCRIPTION OF THE DRAWINGS These and other objects and advantagesof the present invention are more fully apparent from the followingspecification and the appended claims:

FIG. 1 is a side elevational view of the press at the start of the downstroke with the hydraulic system diagrammatically shown in dottedoutline, and only one of each element of each of the three spacersystems being associated with each of the plates of the moving platesystem,

FIG. 2 is a view similar to FIG. 1 and shows the moving plate system atthe finish of the down stroke of the press,

FIG. 3 is an enlarged fragmentary portion of the moving plate system ofthe press, as shown in FIG. 1 but taken from the opposite side, with allof the spacer elements of the three spacer systems shown in place,

FIG. 4 is an enlarged fragmentary portion of the fixed plate system ofthe press as shown in FIG. 1 taken from the opposite of the press,

FIG. Sis a vertical, cross-sectional view taken on line V-V of FIG. 3 ofthe moving plate system of the press,

FIGS. 6, 7, and 8 are views similar to FIG. 5 taken on lines VI-VI,VII-VII, and VIHVIII, respectively, of FIG. 3,

FIG. 9 is a vertical, cross-sectional view taken on line IX--IX of FIG.18 of the fixed plate system of the press,

FIG. 10 is a sectional detail showing the association of a plate and itstension and guide rod,

FIG. 11 is a detail view of the mounting structure for opposite ends ofthe tension and guide rods,

FIG. 12 is a sectional detail of a fixed spacer element,

FIG. 13 is a sectional detail of the back stroke spacer element,

FIG. 14 is a sectional detail of a hydraulic cushion,

FIG. 15 is a sectional detail showing the association of the telescopingpunches with a redrawing die,

FIG. 16 is a fragmentary, elevational view partly shown in brokensection showing the relative positions of the plates of the moving andfixed plate systems of the press at the time of the initial drawingoperation immediately following the shearing of the work blank,

FIG. 17 is a view similar to FIG. 16 showing the commencement of thefirst redrawing operation and illustrating the transfer of the workblank from one punch to the next,

FIG. 18 is a view similar to FIG. 16 showing the work blank through thedrawing operations and partially through the ironing operation,

FIG. 19 is a diagrammatic view of the valve mechanism associated withcertain of the moving plates,

FIG. 20 is a diagrammatic view of the hydraulic systems of the press,

FIG. 21 is a diagrammatic showing of the rogressive forming of the workblank in a modified form of press having five drawing operations and oneironing operation,

FIG. 22 is a diagram view of the pressure pattern of the hydraulicsystem during the stroke of the press forming the work blank of FIG. 21,

FIG. 23 is an enlargement of a portion of the diagram of FIG. 22 moreclearly indicating the pressure impulses,

FIG. 24 is a view similar to FIG. 5 of a modification showing aplurality of telescoping punch sets, and

FIG. 25 illustrates a modified form of support for the moving plates.

The principles of the invention have application to a wide range ofmetals. In practice it has been found possible to deep draw steel,aluminum and brass on the same tools with equal success with onlyadjustments in holddown pressures being required in changing from onemetal to another. Stainless steel, copper, zinc, as well as some of therecently developed space age metals, are also capable of being drawnwith minor changes in tooling and pressure adjustments used for the moreductile metals mentioned above.

BASIC PRESS STRUCTURE When the apparatus for carrying out the improvedprocess of deep metal drawing takes the form of a horizontally disposedhydraulic press, as in the case of the illustrated embodiment of theinvention, the basic structure of the press preferably comprises areinforced concrete base 10 on which a pair of reinforcing and wearplates 12 and 14 are rigidly mounted and constitute the structurereferred to in the appended claims as the supporting surfaces. At oneend of the base is a reinforced cylinder mounting plate 16, and at theother end is located a reinforced press base plate 18.

Plates 16 and 18 are rigidly mounted in any suitable manner on thereinforcing plateslZ and 14 with their opposed vertical faces 20 and 22accurately fiat and parallel to each other and accurately disposed at 90to the plates 12 and 14 which are equally fiat with their upper surfacespreferably disposed in the same plane.

The combination guide rods and tension members 24 are all straight andmutually parallel, and have portions 26 at opposed ends which aremounted in countersunk bores 27 in the faces 20 and 22 with the distancebetween the end portions 26 of each of the members 24 and the depth ofthe bores 27 being held the same, within a few thousandths of an inch,to insure that the plates 16 and 18 are parallel to each other as wellas perpendicular to the members 24. (See FIG. 10.) To enable the members24 to function as tension members as well as spacing members, anysuitable means may be employed for atfixing the ends 26 of the members24 to the vertical plates 16 and 18, such as socket brackets 19 in whichthe ends 26 are received with a close fit, with the ends 26 being tappedto receive the cap screws 21 extending through holes in the plates 16and 18.

MOVING PLATE SYSTEM The moving plate system of the press may take manyforms. One practical arrangement is herein illustrated in which severalplates are provided, one for each drawing punch, a ram plate to whichthe power ram is attached on one side and from which a drawing punchextends from the opposite side, and a plate for the pressure pad and/ora portion of the blanking punch depending on whether presheared blanksor strip or square sheared stock is being run in the press. In thedescription to follow, the press will be described with a blankingoperation being carried on in the press, although it will be understoodthat circular presheared blanks may be loaded in the press and theblanking operation deleted.

In one sense, the moving plates, mentioned in the preceding paragraph,are supported on the guide rods and tension members 24. Morespecifically, the ram and punch plate 28, punch plates 30 and 32, andblank and pad plate 34 are all provided with openings 36 in whichbushings 37 are inserted, the openings 36 being preferably provided atthe four corners of the plates with the members 24 being received withinthe tushings 37 with a close sliding fit. Clamps 37 hold the bushings 37in place. (See FIG. 9.)

Each of the plates 28, 30, 32 and 34 is provided at its lower cornerswith suitable support members 38 capable of sliding or rolling on thereinforcing and wear plates 12 and 14. Preferably, the members 38 arelocated and removably attached at the lower opposite corners of theaforesaid plates and are adjustably related to their associated platesthrough the use of shims, and the like, to permit fine verticalregulation to bring about the desired situation in which the members 24support the plates 28, 30, 32 and 34, and these same plates in anothersense support the members 24.

SPACER MEANS FOR THE MOVING PLATE SYSTEM which are imposed betweenadjacent plates to determine the minimum spacing between such plates onrelative approach movement. Another system of spacers is connectedbetween adjacent plates for returning the plates to their relativepositions at the conclusion of the back stroke of the press. Thesespacers will be called back stroke stop spacers. The third system ofspacers preferably takes the form of hydraulic cushions which areimposed between adjacent plates 28, 30, 32 and 34 and have two differentoperation states, a locked state in which they function as a rigidthrust column structure between adjacent plates and a regulated stateduring which the effective length of the cushion as a spacer is reducedunder the control of valving means to permit regulated relative approachmovement between adjacent vertical plates.

In the interest of rigidity, augmentation of parallelism, maintenanceand accessibility for adjustment, each of the three types of spacersmentioned above is completely independent in structure and functionsfrom the other. However, it is anticipated that two or more of thesethree systems may be combined into a single system capable of performingthe same functions as the three systems described in the precedingparagraph.

To describe each of the three spacer systems in more specific detail andwith respect to the illustrated embodiment of the invention, the down"stroke stop spacers in their simplest form may be no more than a blockof steel, as indicated at 40, having the vertical faces thereof atopposed ends parallel with each other. Each plate 30, 32 and 34 isprovided with a plurality of such blocks preferably equally disposedabout the longitudinal axis aa of FIG. 1, only one of such blocks beingshown in FIG. 1 associated with each said plate, for purposes ofclarity. In practice, the vertical faces of each of the plates 28, 30,32 and 34 are machined parallel to each other with a high degree ofaccuracy. As the vertical faces of each of said plates are also parallelto the corresponding opposite faces of adjacent said plates, thisarrangement permits all the down stroke stop spacers 40 associated withthe same adjacent plates to be of the same identical length. Themounting of the spacers 40 to the vertical face of one of the adjacentpair of plates may be done in any suitable manner, such as by a capscrew 41 located in a horizontal hole in the plate to which the spacer40 is attached and engaged in a threaded hole in one of the abutmentends of the spacer 40, as shown in FIG. 11. In this manner the verticalface on one end of each spacer 40 may be rigidly clamped to the verticalface of its associated plate, and the opposite end of the spacer 40presents an abutment surface which is parallel to the surface of theplate with which that end of the spacer 40 engages. The simpleattachment arrangement of each spacer 40 to its associated plate alsoprovides for the convenient use of washer-like flat shims of the samethickness to be disposed between the spacer 40 and the face of the plateto change the effective length of each spacer 40 associated with thesame plate.

The specific structure of the back stroke stop spacers for locating eachplate 30, 32 and 34 relative to each other, as well as relative to theplate 28, at the conclusion of the back stroke of the press, may takemany and varied forms. Such spacers are indicated at 42 and they are ofa design that does not interfere with the relative movement of thevertical plates with respect to each other during the down stroke of thepress, yet on the back stroke of the press the spacers 42 act as themeans for returning the plates 30, 32 and 34 in definite relationship toeach other on the return of the ram plate 24 at the conclusion of theback" stroke of the press.

In the illustrated form, each spacer 42 comprises a rod 44 fixedlyattached in any suitable manner at one end to a plate of the movingplate system of the press and having a free sliding fit in a bushing 46carried on and aligned with opening 48 in an adjacent plate. Abutmenthead 50, preferably adjustable by use of shims between head 50 and rod44, is attached to the opposite end of the rod 44.

When adjacent plates approach each other on the down stroke of thepress, the rod 44 will slide through the bushing 46 in opening 48 withrelative movement taking place between the head 50 and the outer face ofthe bushing 46. On the back stroke of the press, movement of the ramplate 28 will provide the necessary relative movement for the head 50 tobe engaged by the outer face of the bushing 46. On such engagementbetween the opposed faces of the bushing 46 and head 50, the rod 44 willbe tensioned and the movement of one plate will be progressivelytransferred to the next adjacent plate.

The spacers 42, associated with adjacent plates of the moving platesystem, are preferably equally disposed about the longitudinal axis a-aof FIG. 1, as in the case of the spacers 40. Each spacer 42 associatedwith each pair of adjacent plates is preferably of substantially thesame effective length so as to complement the parallelism of the plates30, 32 and 34.

By having the rods 44 of equal effective length and parallel to theguide rods and tension members 24, as well as to each other, and havingthe abutting faces of the bushings 46 and heads 50' parallel to eachother and to the faces of the moving plates, movement of the plates 30,32 and 34 by the ram plate 28 on the back stroke of the press isaccomplished without disturbing the parallelism of the components of thepress. It will be appreciated that flexible cables or chains of theproper lengths may be attached between adjacent members of the movingplate system of the press which would perform a function similar to thatattributed to the rods 44 and associated structure as above described,except for the guide pin effect of the rods 44.

HYDRAULIC CUSHIONS The third spacer system of the press is more complexas to both structure and function than the systems of the spacers 40 and42. Because of this fact, the hydraulic cushions which characterize thespacer means of the third system, although all are similar in functionand construction (as in the case of spacers 40 and 42) each set ofcushions associated with each of the plates 28, 30 and 32 will beidentified and described through the use of separate referencecharacters.

In general, each cushion comprises a cylinder which is fixedly mountedon its associated plate of the moving plate system and functions as anintegral part thereof. As a functional part of each cylinder, a pistonis provided which extends into the cylinder as well as out of thecylinder. That portion of the piston which projects from the cylinderperforms the function of a thrust member of adjustable length whichspaces the plates of the moving plate system as well as controls theirrelative sequential movement in an approaching direction on the downstroke of the press. The cylinders of the set of hydraulic cushionsassociated with each of the above-mentioned plates are preferablyequally distributed about the longitudinal axis aa, as in the case ofthe spacers 40 and 42.

In specific detail, one set of hydraulic cushions 52 is mounted on theplate 28, another set of cushions 54 is mounted on the plate 30, and athird set of cushions 56 is mounted on the plate 32. Each set ofcushions 52, 54 and 56 comprises cylinders 58, 60 and 62, and pistons64, 66 and 68, respectively. It will be noted that the cushions of eachset are the same as to length, and that each set of cushions isdifferent from the other as to length. The difference in length of thecushions is determined by the necessary spacing of the plates of themoving plate system when that system is being advanced by the ram as athrust column of constant length. As will be hereinafter described inmore detail, hydraulic fluid is admitted to the cylinders 56, 60 and 62to act on the ends of the pistons 64, 66 and 68, respectively, to extendthe pistons 64, 66 and 68 to their extended positions, which positionsare preferably determined by the effective lengths of the spacers 42.Thus, fluid pressure in the cushions 52, 54 and 56 acts to 8 place therods 44 of spacers 42 under tension by acting to separate plates 28, 30,32 and 34.

When the hydraulic fluid is trapped in the cushions 52, 54 and 56 bysuitable valve means, the pistons thereof will function as relativelysolid thrust columns disposed between the plates 28, 30, 32 and 34. Byregulating the flow of fluid from the cushions by suitable valve means,the cushions will collapse and the effective length of the pistons 64,66 and 68 will be reduced to permit the plates of the moving platesystem to approach each other.

It should be understood that the ram pressure of the press is impressedon the metal forming tools of the press through the hydraulic cushions52, 54 and 56. When the cushion 56 has collapsed to the point at whichthe spacers 40 on plate 34 abut the plate 32, the limit of relativeapproach movement between the plates 32 and 34 has been reached.Likewise, when the cushion 54 has collapsed to a point at which thespacers 40 on plate 32 abut the plate 30, the limit of relative approachmovement between the plates 32 and 30 has been reached. A similarsituation exists when the collapse of the cushion 52 permits the spacers40 on the plate 30 to engage the plate 28. On sequential collapsing ofthe cushions 52, 54 and 56, the working load being applied to the metalforming tools will be transferred by the locked cushions and thecollapsing cushions will hold the plates ahead in the moving platesystem together when they have reached their position of completeapproach, which position is determined by the spacers 40 being engagedby adjacent plates. The further function of the cushions 52, S4 and 56will be described in connection with the function of the punches of theplates of the moving plate system as pressure pads.

TELESCOPING PUNCHES Each of the plates 28, 30 and 32 supports a tubularpunch 70, 72 and 74, respectively, the punches being nested one withinthe other with a close sliding fit. As the punches will normally be oftool steel, to avoid a galling, that may be experienced with asteel-to-steel fit, nonferrous bushings 75 are preferably employedbetween the punches.

The amount of reduction in the diameter of the work blank betweendrawing operations is such that the tubular punches 70, 72 and 74 havesuflicient wall thickness to make them structurally rigid. They arerigidly connected to their respective plates of the moving plate systemin any suitable manner with their longitudinal axes being common to theaxis a-a of FIG. 1. As shown each punch 70, 72 and 74 has a series oftapped holes 76 at its inner end for receiving screws 77 for attachingthe punches to the plates. The plates 30, 32 and 34 have openings 78concentric with the punches to permit the telescoping assembly of thepunches to extend through the plates with clearance, as well aspermitting the plates to have relative approach movement.

When the press is at the end of its back stroke and in the position fromwhich the down stroke is initiated, the forward ends 80, 82 and 84 ofthe punches 72 and 74, respectively, are preferably disposed in theslightly stepped position shown in FIG. 4. This arrangement permits aslight amount of creeping of the punches relative to each other withoutthe tendency to crown the bottom of the metal article being obviated.The stepped arrangement of the punches has the further advantage ofproviding a slight amount of lag in the sequential functioning of thepunches so as to make the timing of the punch movement less critical.

FIXED PLATE SYSTEM The number of plates in the fixed plate system andthe tools mounted on the plates thereof will usually be determined bythe number of plates in the moving plate system and the article that isto be formed by a single continuous stroke of the press. If blanking isto take place in the press, then the first fixed plate will mount theblanking operation as well as the first draw. The following fixed platesmay be tooled for a redrawing or ironing operation or a combinationthereof. If the metal article being formed is to have a detailed bottom,then the innermost punch of the telescoping punch assembly will beshaped on its outer end to perform the detailing operation incooperation with a detailing die carried by the last fixed plate, or thebase plate 18, as may be desired. Preferably, the base plate 18 isapertured to enable the same to carry a drawing or ironing die, as wellas a stripper mechanism where detailing of the bottom of the formedarticle is not to be performed.

In the illustrated form of the invention, the fixed plate system of thepress comprises the plates 86, 88, 90 and 92, all having clearance holes94 therein of different sizes with their centers located on the axisa--a of FIG. 1. The fixed plates are of rigid construction and areprovided with holes 36 at their four corners with bushings 37 to receivethe guide and tension members 24 with a close sliding fit so as topermit adjustment of the fixed plates along the members 24. As in thecase of the plates of the moving plate system, rigidity, parallelism andconcentric alignment is important. To that end the vertical faces ofeach plate 86, 88, 90 and 92 are parallel to each other, as well as tothe faces of the other fixed plates. Located between each of the plates86, 88, 90 and 92 and between the plate 92 and the base plate 18 aresets of spacers 98 equally distributed about the axis a-a of FIG. 1. Thespacers 98 have a length which depends on the necessary spacing of theplates to form the metal article and they usually are of increasinglength in the direction of the down stroke of the press. However, thespacers 98 of each set are preferably of the same length so as to holdthe plates 86, 88, 90 and 92. parallel with the ends of the spacers 98abutting the opposite vertical surfaces of adjacent plates. Cap screws100 may be employed to connect the plates 18, 86, 88, 90 and 92 into arigid complex of parallel plates horizontally aligned on the members 24,as well as being vertically supported from the supporting surface of thebase of the press through adjustable leveling screws 101.

BLANKING, DRAWING, IRONING AND DETAILING DIES When a circular blank isto be punched from strip stock or square cut stock S, a blanking punch102 in the form of a flat ring is mounted on one face of the plate 34 inany suitable manner. The blanking die 104 is mounted on the oppositeface of the fixed plate 86 and takes the form of an annulus whichpresents a shearing edge to the blank punch 102. The first draw die 106is nested within the blanking die 104. A flat vertical face 108 on thedrawing die 106 provides a hold down surface with which the fiat surface109 of the blanking punch 102 co-acts as a pressure pad to control themarginal portion of the sheared blank B during the first draw operation.In all of the following redrawing operations, the telescoping punches ofthe press perform the function of pressure pads on the progressivelydrawn work blank B.

Plates 88 and 90 are shown with redraw dies 110 and 112, respectively,while the plate 92 has an ironing die 114 on one side and a strippermechanism 116 on the opposite side. A die 118 is shown mounted on theinside surface of the base plate 18 for detailing the bottom of a metalarticle being formed. It will be understood that the work blank will becarried through the redrawing die 112 and the ironing die 114 on thepunch 70 mounted on the moving plate 28. Also, the punch 70 will detailthe bottom of the work blank in the die 118 at the end of its downstroke, and the completed work blank will be stripped off the punch 70by the mechanism 116 on the back stroke of the press.

The punch 74 mounted on the moving plate 32 will continue through thedrawing die 106 to its fully approached position relative to theredrawing die 110, at

which position the end 84 will perform the function of a pressure pad inconjunction with the face 111 of the die 110. When the travel of thepunch 74 is arrested by spacer 40 on plate 34, the punch 72 on themoving plate 30* will draw the work blank in the redrawing die andcontinue to its fully approached position relative to the redrawing die112, in which position the end 82 of the punch 72 will perform thefunction of a pressure pad.

CONTROL OF PRESSURES AND STRESSES ON WORK BLANK The present invention isprimarily concerned with the deep drawing of metal articles withoutannealing in which the ratio of height to diameter of the work blank atthe conclusion of the drawing operation, performed during a singlecontinuous stroke of the press, is substantially greater than has beenheretofore performed in commercial practice. A ratio of height todiameter exceeding 4 to 1 and up to 8 to 1 has been obtained underpractical commercial operating conditions. When one or more ironingoperations are performed in the press following the last redrawingoperation, the ratio of height to diameter of the work blank may readilybe in the order of 8 to 1 through 15 to 1. Thus, it will be appreciatedthat the telescoping punches will of necessity be of extreme length inorder to perform the drawing, ironing and stripping operations in thefixed plate area of the press. This is especially true where thediameter of the finished metal article exceeds six inches.

Due to the heat generated by the drawing and ironing operation performedby a single and continuous stroke of the press, thermal expansion of thepunches Will take place which will affect the performance of the press.When the press has been out of operation for any substantial length oftime and the temperature of the telescoping punches has returned tosubstantially room temperature, adjustment of the spacers of the pressat that time to correctly locate the ends of the punches relative to thedrawing dies will result in an improper adjustment when the punches arebrought up to the temperature at which the punches obtain duringprolonged operation of the press. To avoid this situation, an elongatedfully enclosed thermostatically controlled electrical resistant heatingunit 120 is shown located within the innermost punch 70 of the assemblyof the telescoping punches. The unit 120 is shown connected to anelectrical outlet 122 for convenient attachment to a source ofelectrical energy when the press is not in operation. In this manner thepunches are maintained at a temperature corresponding to the operatingtemperature and start-up adjustments are avoided.

According to the invention the work blank B in all drawing operations ispreferably drawn over a relative gradual radius 124 with minimumclearance being provided between the drawing die and the punch, ascompared to standard practice, to cause the Work blank to have an insidediameter, very close to the outside diameter of the punch, preferably,to the point of punch hugging. In practicing the invention, it has beenfound that the clearance 126 between the drawing die and the punch ineach drawing operation may be the same and good results are obtainedwhen this clearance is in the order of 60-70 percent of the clearancerecommended by standard handbook practice with light gauge material. Forexample, whereas standard practice may call for a clearance at 126 of2.3 times the thickness of the stock being drawn, according to thepresent invention the clearance used is, preferably, in the order of 2.2times the thickness of the stock.

Whereas it has been thepractice heretofore to increase the clearance 126in subsequent redrawing operations because of the tendency of the workblank to thicken at the top during each following drawing operation, theobjects of the present invention are best obtained by maintainingsubstantially the same clearance 126 in all subsequent redrawingoperations, and effecting at least a slight amount of ironing action onthe top area of the work blank in each drawing operation.

The ironing operation, mentioned in the preceding paragraph, at the topof the work blank, results from the fact that the reduction in clearanceover standard practice provides an interference fit between the punchand drawing die and the thickened top portion of the Work blank.

During the sequence of drawing operations being carried out inaccordance with the present invention by a single continuous stroke ofthe press, the top area. of the work blank that is ironed will begreater in each successive drawing operation.

As will be more fully discussed hereinafter, the process of the presentinvention results in what appears to be a reduction in the amount and/or the rate of work and strain hardening of the work blank in obtainingthe same reduction in blank diameter heretofore experienced undergenerally accepted commercial practice. Under the practice of thepresent invention, in addition to the apparent lower rate of work orstrain hardening, a high degree of uniformity of work hardening ismaintained circumferentially of the work blank with the avoidance ofoverworked localized areas which would have a tendency to initiate metalrupture in following redrawing operations, or would necessitateannealing of the Work blank before performing secondary operations onthe work blank B after removing the same from the press. In thefollowing paragraphs the structural factors which are believed tocontribute to the circumferential uniformity of the work or strainhardening of the work blank are reviewed:

The initial movement of the moving plate system along the guide andtension members 24 rigidly couples the same to the rigid mass of thefixed plate system through the medium of the guide pins 128 on themoving plate 34 entering the bushings 130 in the fixed plate 86 with aclose tolerance sliding fit. As the drawing operations are being carriedout in sequence in the press, the mass of the moving plate system isbecoming more compact as it moves toward the area in which the drawingoperations are being carried out. This increase in compactness is due tothe relative approaching movement of adjacent moving plates under thecontrol of the hydraulic cushions and has the effect of augmenting therigidity, parallelism, and concentricity of the components of the movingplate system.

The telescoping association of the punches of the press, coupled withthe rigid parallelism of the moving plate system which supports thepunches, results in the punches being concentrically presented to thedrawing dies with a high degree of accuracy. This concentric relationbetween the punches and the dies is maintained throughout the severaldrawing operations performed in the press during a single continuousstroke thereof. As a result, excellent control of the metal of the workblank becomes a possibility when this relationship is combined with themovement of the work blank from one punch, with pilot action, throughthe drawing die and back on the next punch. This factor plus a tendencytoward punch hugging of the work blank and the ironing of the top areaof the work blank in each drawing operation, all seems to contribute tothe circumferential uniformity of the work or strain hardening of thework blank.

With highly polished drawing dies in a process having the structural andfunctional features described above, total reduction of blank size inthe order of 80% has been successfully carried out during a singlecontinuous stroke of the press under conditions of commercial practicewith out metal rupture, and at the conclusion of the drawing operationseffecting such a high reduction, the metal of the work blank is stillcapable of withstanding forming operations on the open end of the workblank, such as a beadingoperation, without first annealing. Also, it hasbeen possible in the practice of the present invention to havesuccessive reductions in the redrawing operations,

each in the order of 25% to 30% in lieu of the practice of carrying outreductions in redrawing on a severe sliding scale such as 25%, 15% and10%.

In the light of the results obtained by the present in vention, it ispractical to have a reduction in the first drawing die 1% in the orderof 40% and to perform redrawing in each of the drawing dies 110 and 112with reductions in the order of 25%. Using three redrawing dies, thispractice will give a total reduction in blank sizes without annealing ofapproximately and if four redrawing operations are used, the totalreduction may be in excess of These results may be compared withstandard practice giving total reduction possible under conditions ofcommercial practice in the order of 55% before annealing.

Another area of departure of the process herein disclosed over standardpractice relates to the speed of drawing the metal in the press.Whereas, heretofore conventional practice has indicated speeds in theorderof 45 feet to 70 feet per minute, excellent results have beenobtained according to the invention with drawing speeds in the order offeet per minute.

RATE OF WORK OR STRAIN HARDENING It appears that in the process of metalforming as carried out in accordance with the present invention the rateof work hardening is materially reduced over the rate that isexperienced when the same work blank is processed over the same toolsbut with an interruption between each operation in lieu of all theoperations being carried out during a single continuous stroke of thepress.

In an effort to establish the reduction in the rate of work hardening,numerous microphotographs have been taken of work blanks which have beensheared and drawn from the same strip of stock as produced at themilhSome of these work blanks were drawn in a press constructed andoperated accordingto the invention by being completely for-med by asingle continuous uninterrupted down stroke of the press. Other workblanks were formed by interrupting the down stroke of the same pressafter the first drawing operation and then thereafter completing thefollowing drawing operations. Some of these blanks were removed from thepress following the first drawing operation and were then transferred toconventional drawing tools to complete the drawing operations, thereductions of the conventional drawing tools corresponding to those ofthe omitted drawing operations in the press of the invention, wherebythe total amount of deformation of the metal would be substantially thesame in the articles completely formed in the press of the invention asin the articles partially formed in such a press and then completed onconventional tooling.

The remaining workability of the work blanks processed according to thepresent invention, as compared to the work blanks finished onconventional tooling, clearly suggests a lower rate of work hardening.However, the comparison of grain structure in microphotographs hasfailed to fully account for the substantial increases in remainingworkability of the work blank and the substantial increase in totalreductions that can be obtained in commercial practice by following theteaching of the present invention.

It should be appreciated that the availability of the remainingworkability of the work blank at the conclusion of the drawing andironing operations is of great commercial importance when secondaryoperations are to be formed on the metal article. This availableworkability enables such operations to be performed directly on removingthe article from the draw press and without the necessity of subjectingthe same to an annealing operation.

13 CONTROL SYSTEM FOR HYDRAULIC CUSHIONS It will be appreciated thatwith the sets of hydraulic cushions 52, 54 and 56 mounted on and movingwith the plates 28, 30 and 32 of the moving plate system of the press,the supply of hydraulic fluid to and from the cushions and the controlof hydraulic fluid pressure in the cushions during unitary as well asrelative movement of such plates should be carried out, if possible,without resorting to an involved hydraulic system which would materiallyincrease the cost of the press and its maintenance. The quantity ofhydraulic fluid required in large size presses of the type contemplatedby the present invention and the rapidity with which the fluid must betransferred relative to the cushions during the operation of the press,without overheating or foaming of the fluid, aggaravtes the problem.

First, it should be noted that the hydraulic system for the fiow offluid to and from the supply and the control of the hydraulic cushionsis separate and distinct from the hydraulic system that may be employedto actuate the ram on the down and back strokes of the press. This istrue, although the forces exerted by the ram on the moving plate systemcreate the working pressure in the hydraulic cushions.

Preferably, the hydraulic fluid employed in the hydraulic cushions 52,54 and 56 is transferred between the cylinders 62 and the supply 132through large size flexible hose lines 134 which are attached at one endto the valve structure of the moving plates 28, 30, 32 and 34 and attheir opposite ends to one or more suitable supply tanks. These linesare supplied and supported in such a manner as to avoid abrasion astheir ends attached to the plates travel back and forth during theoperation of the press.

To eliminate as much piping and external manifolding as possible, eachof the moving plates 28, 30, 32 and 34 has passages 136 and they eachact as a manifold for delivery of hydraulic fluid to the set of cushionsassociated with each of these plates. Mounted on top of each of theported plates is a hydraulic manifold 138 for the hydraulic connectionof the passages 136 of the plates with a main control valve 140. Plates30 and 32 carry pressure switching valves 142 on their sides. Each ofthe mentioned valves has a manually actuated knob 144 for effectingpressure changes. In the operation of the press of the presentinvention, it is usually only necessary to make adjustments in pressuresthrough manipulation of the knobs 144 in changing from one material toanother of the same gauge. Aluminum, brass and steel articles, forexample, fabricated from stock of the same gauge have been successfullydrawn over the same dies by merely changing the operating pressures ofthe hydraulic cushions 52, 54 and 56 associated with the moving platesof the moving plate system.

Each of the passages 136 of the plates of the moving plate system has aconnection with the longitudinally extending passage 148 in each piston68 of each hydraulic cushion. The outer end of each piston 68 has asealed connection with the passage 136 in the plate to enable hydraulicfluid to flow to and from the cylinder 62 through the passage 148 in thepiston 68. When the fluid is trapped or locked in the cylinder 62 by thevalve 142, each cylinder 62 and each piston 68 will collectivelyfunction as a thrust column of fixed length between adjacent plates ofthe moving plate system. When the valve 140 is triggered by the pressureswitching valve 142, as will hereinafter be described in more detail,the fluid is metered from the cylinder 62 through the passages 148 and136 and the piston and hydraulic cushion collectively defined by thecylinder 62 and piston 68 will collapse under controlled conditions toenable adjacent plates of the moving plate system to approach eachother.

14 SWITCHING VALVE FUNCTION In order to more fully describe the functionof the switching valves 142, let it be assumed that the hydraulicpressure system for operating the ram 150 is capable of exerting 50 tonsof force on the ram 150, which force is in turn directed through thesemirigid connection 152 to the plate 28. The main valve 140 under theconditions assumed would be adjusted to maintain in excess of 50 tons offorce, or a pressure such that each of the four hydraulic cushionsassociated with each of the plates 28, 30 and 32 is capable of exertingback pressure in excess of 12.5 tons.

At this point it should be noted that preferably the main control valve140 of the plate 34 does not have a switching valve 142 connected to it.Instead, it is a self-contained pressure regulating valve and functionsto maintain a constant pressure in the cushions of the set of cushions56 disposed between the plates 32 and 34 sufiicient only to hold thesheared work blank B from wrinkling while the first drawing operation isbeing performed.

Let it be assumed that the valve 140 of plate 34 is set at a pressure atwhich the set of four cushions 56 will exert a total of 15 tons ofhold-down pressure available in the pressure pad structure in the firstdrawing operation. This 15 tons of pressure is constant and it will bemaintained through the entire first drawing operation. When the 15 tonsof hold-down pressure is substracted from the 50 tons of available forceof the ram 150, the remaining 35 tons is available for the first drawingoperation with the ram 150 delivering only the amount of force resistingits down stroke movement. It will be understood that a constant backpressure in the order of 20 to pounds per square inch is imposed on thehydraulic fluid supply 132 which keeps the hydraulic cushion full offluid and the valves of the hydraulic system of the hydraulic cushionsin a working condition. When the hydraulic cushions are full of fluidand such fluid is locked or trapped therein, it causes each of thehydraulic cushions 52, 54 and 56 of the set located between the plates28, 30, 32 and 34 to function as a thrust column of fixed length untilthe movement of the plate 34 is arrested and the pressure of the ram 150on the moving plate system overcomes the pressure setting of the valveon the plate 34, thereby causing the fluid trapped in the set ofcushions 56 to be expelled therefrom permitting the plate 32 to approachthe plate 34.

As the moving plate system is advanced as a unit by the ram at the startof the down stroke of the press, the guide pins 128 on the plate 34enter the bushings 130 on the plate 86 to rigidly couple the plate 34 tothe plate 86 just before the blanking punch 102 engages the strip stockS and forces the stock S against the cutting edge of the blanking punch102. The cutting edge of the blanking punch 102 must have enough shearangle on it to allow the strip stock S to be blanked with a force lessthan 15 tons, otherwise the set of cushions 56 will start to collapseand the work blank will be engaged by the punch 74 before the work blankB is completely sheared and the face 109 of the blanking punch is in aposition to function as a pressure pad.

Assuming the plates 34 and 86 have approached each other to complete theshearing of the work blank B from the strip stock S and the face 109 ofthe blanking punch 102 carried on plate 34 is exerting 15 tons ofpressure on the marginal portion of the work blank B sheared from thestrip stock S, the spacers 40 located between the plates 34 and 86 havebecome effective and have limited the approach movement of the plate 34toward the plate 86. By so doing, the spacers 40 have stopped the plate34 in a position spacing the face 109 of the blanking punch 102 from theface 108 of the first drawing die 106 on the plate 86 a distanceapproximating the thickness of the strip stock from which the work blankB has been sheared. This function of the spacers 40 provides stoparrested blank-holding for the workpiece or blank.

With the unitary movement of the moving plate system having advanced allthe plates 28, 30, 32 and 34 to the point at which the spacers 40,between the plates 34 and 86, have arrested further down stroke movementof the plate 34, the set of cushions 56 which has been spacing theplates 32 and 34 will start to collapse under the force being exerted bythe ram 150 which is in excess of the 15 tons of pressure pad actionbeing exerted on the spacers 40 between the plates 34 and 86. Thispressure reacts against any tendency for the marginal portions of thesheared work blank B to wrinkle and thicken during the first drawingoperation. Under the influence of such pressure the face 109 of theblanking punch 102 provides pressure blank-holding for the workpiece orblank.

As the set of cushions 56 collapses, hydraulic fluid in the cylinders 62will be forced out through the longitudinal passages 148 in the pistons68 into the passage 136 of the plate 34 and through the control valve140 to the supply 132, the flow of fluid between the valve 140 and thesupply 132 being against the supply pressure created by the air pressureof 400 pounds per square inch upon the hydraulic fluid in the supply132.

With the initial collapsing movement of the cushions 56, the plate 32and its associated drawing punch 74 will be advanced to move the punch74 into contact with the sheared work blank B imposed on the face 108 ofthe drawing die 106 carried on the fixed plate 86 of the fixed platesystem. With the unitary movement of the moving plate system nowconfined to the plates 28, and 32, the continued down stroke of the ram150 will start the first drawing operation by advancing the punch 74through the drawing die 106 of the plate 86.

In FIG. 16 the relative positions of the plates 32, 34 and 86 is shownwith the first drawing operation partially complete. The extent that theplate 32 has approached the plate 34 is indicated by the distance thehead 50 of the back stroke spacer 42 has been projected from the face ofthe bushing 46 supported on the vertical face of the plate 32. It isalso to be noted that the pressure switching valve 142 carried on theplate 32 is approaching its actuator 154 on the plate 34.

FIG. 17 shows the relative position of the plates 32, 34 and 86 afterthe completion of the first drawing operation and at the start of thefirst redrawing operation in the drawing die 110 carried on plate 88.The spacers 40, between the plates 32 and 34, are new active to limitthe down stroke approach of the plates 32 and 34, the collapse of thecushions 56 having terminated, and the pressure switching valve 142having engaged its actuator 154 on the plate 34 to unlock the fluid inthe set of cushions 54 spacing the plates 30 and 32. Collapsing actionof the cushions 54 will initiate the first redrawing operation as thedown" stroke of the moving plate system, now confined to the plates 28and 30, continues.

It is in connection with the first redrawing operation that the drawingpunch 74 of the first drawing operation takes on the dual function of apilot and a pressure pad for the following drawing operation. This dualfunction has been described in detail heretofore in regard to that shownin FIG. 15. To function properly as a pressure pad, the end 84 of thepunch 74 must be maintained a proper distance from the face 111 of thefirst redrawing die 110. It is one of the functions of the spacerslocated between the plates 32 and 34 to provide such spacing. As thelength of the spacers 40, between the plates 32 and 34, is determinedwithout regard to the longitudinal thermal expansion of the punch 74,pinching of the work blank may result of a magnitude that will causerupture of the work blank during the first redrawing operation. It isfor this reason that it may be found desirable, as herein proposed, tomaintain the telescoping punch assembly at a controlled temperature atall times to avoid start-up adjustment or metal rupture from thermalexpansion when operating temperatures have been reached in a productionrun.

CLEARANCE HOLES IN MOVING PLATE SYSTEM As heretofore mentioned, for thesake of clarity, in FIGS. 1 and 2 only one spacer element of each of thethree spacer systems for the moving plate system has been illustrated.However, in FIGS. 3, 4, 15, 17 and 18 such spacer elements are all shownin the actual number used in the press and as they appear in sideelevation.

In FIGS. 5, 6, 7 and 8 these cross-sectional views are taken on thesectional lines of FIG. 3 so that the spacer elements omitted in FIGS. 1and 2 all appear in FIGS. 5, 6, 7, 8, 16, 17 and 18.

Of the elements of the three spacer systems shown in FIGS. 12, 13 and14, only the spacer elements of FIGS. 13 and 14 necessitate that theplates 28 and 30 of the moving plate system be provided with clearanceholes in order to permit the plates 28 and 30 to move from the positionof FIG. 1 to the position of FIG. 2 on the down stroke of the press.

In FIG. 7 is shown clearance holes 50 for the heads 50 of the spacers 42attached to the plate 32. Also, in FIG. 7 is shown the clearance holes56 in the plate 30 to permit passage of cylinder 62 of the cushions 56mounted on the plate 32. FIG. 8 shows the clearance holes 54' in theplate 28 for the passage of the cylinders 60 of the cushions 54 mountedon the plate 30.

FIGS. 5, 6 and 7 indicate the distribution on the plates 30, 32 and 34of the spacer elements of the three systems illustrated in FIGS. 12, 13and 14. The elements are shown as being used in sets of four associatedwith each of the plates 30, 32 and 34. Preferably, they are as equallydistributed as possible about the axis aai and in this manner assist inmaintaining parallelism of the plates 28, 30, 32 and 34. Obviously, thenumber of spacer elements in each set may be varied as may theirlocation on the plates.

MULTIPLE SETS OF TOOLS The design of the press of the present inventionlends itself to unlimited enlargement of the plates carrying the diesand punches Where it is desired to produce more than one drawn articleduring each stroke of the press. For example, to adapt the press to theeconomical manufacture of inexpensive seamless cans for use in thepackaging of food and beverages, a great many sets of telescopingpunches could be mounted on the plates of the moving plate system of thepress with corresponding sets of dies located in the fixed plate systemof the press. In lieu of the plate 28, for example, carrying only onepunch 70, it could carry a great many punches, the number depending onthe size of the can to be drawn and the practical and economicallimitation on the size of the press.

FIG. 24 illustrates a modified form of the invention in which three setsof telescoping punches are shown installed in the press in lieu of thesingle set of telescoping punches employed in the form of the inventionof FIG. 1. FIG. 24 is a cross-sectional view corresponding substantiallyto FIG. 5. It Will be noted that the sets of punches each comprisespunch '72 and 74, and that these sets are grouped around the centralaxis of the plate 34 in lieu of being located concentric with the axisin the manner of the single set of telescoping punches of FIG. 5. Theprimed reference characters of FIG. 24 indicate the same partsdesignated in FIG. 5 with corresponding unprimed reference characters.

THEORIES OF THE INVENTION In order to provide a possible explanation forthe unexpected results obtained in the commercial practice of thepresent invention in the production of metallic articles fabricated fromsheet metal by a single continuous uninterrupted stroke of the press,such articles have been fully investigated through the use ofmicrophotographs, by residual stress analysis, and determination ofmechanical properties.

For the purpose of making comparison between articles fabricated byemploying the invention and articles fabricated in accordance with wellestablished commercial practices heretofore employed, every possibleprecaution has been taken to obtain substantially identical test blanks.Such blanks have been drawn on substantially identical tooling, one setof tooling being employed in a press constructed according to theinvention and another set of tooling being used in conventional drawingpress apparatus.

In analyzing the results obtained in comparative tests, metal rupture,metal splitting, degree of work hardening, remaining workability of thedrawn article and uniformity of mechanical properties have all beenfactors of principle importance for consideration from a commercialpoint of view.

As heretofore stated, the studies that have been made in regard tocomparative tests have indicated that there has been a reduction in thedegree of work hardening (in terms of remaining workability) in thefabrication of metallic articles in accordance with the principles ofthe present invention, as compared with the amount of work hardeningthat is experienced when metallic articles are subjected to the sameamount of metal deformation when carried out in accordance with existingconventional practices.

Investigation as to residual stresses appears to indicate that the pressand process of the present invention tends to minimize the accumulationof residual stresses of a nature detrimental to deep-drawing of metallicarticles.

Example No. 1

This test was conducted on sheet metal blanks certified by the metalproducer as being substantially identical in all respects. The blanksize was 12.25, the stock thickness .045, the material 1008 low carbondraw quality steel, and the finished can had an outside diameter of 4and a height of 8 /4". The first draw die, first redraw die and secondredraw die and radii of A1, A and /2", respectively, while thecorresponding punches had diameters of 6.73", 4.82" and 3.91",respectively.

Sample D.-Blanks according to the preceding paragraph were placed in apress constructed according to the invention and having a set of nestedpunches consisting of the three punches indicated above. The cans wereformed with one continuous uninterrupted stroke of the press, the speedof the stroke being approximately 50 feet per minute. Punch and dieclearances and all other constructional and functional features of thepresent invention, as heretofore set forth in this specification, wereobserved in this test. The drawn articles resulting from the test showedno splitting or metal rupture and were otherwise completely satisfactoryas to finish, lack of surface defects and other qualities required ofdrawn metallic articles for commercial purposes.

Sample D31.-The procedure set forth under Sample D was modified bystopping the press at the completion of the first draw and removing thecan from the first draw punch. Eighteen hours later the can in the samecondition as it was when it was removed from the punch was installed onthe first draw punch and the down stroke of the press was continued tocomplete the first and second redrawing operations. In every casesplitting of the can was experienced at the top of the can, the splitsoccurring, for the most part, in the valley between the eating on theupper edge of the can and generally taking place at the time ofstripping of the can from the punch, indicating excessive work hardeningwith a resulting brittleness that would not withstand the action of thejaws of the conventional stripping mechanism.

Example No. 2

The conditions were the same as set forth in Example No. 1, except thematerial being tested was low carbon aluminum killed steel in lieu ofdrawing quality steel.

Sample K21.Procedure was the same as in Sample D of Example No. 1 withthe same result, namely, no splitting or metal rupture.

Sample K29.Procedure was the same as in regard to Sample D31 of ExampleNo. 1 with the same result, namely splitting of the can was experienced.

Example No. 3

The conditions were the same as set forth in Example No. 1 except thematerial was commercial quality low carbon steel.

Sample C.Procedure was the same as in the case of Sample D of ExampleNo. l with the same result, namely, no splitting or metal rupture.

Sample C27.Procedure was the same as in Sample D31 of Example No. 1,with the same result, namely, splitting of the can.

Example No. 4

A test was run on a press constructed and operated in accordance withthe invention, the press being one used in regular commercialproduction. In this press the moving plate system comprises a set offive telescoping punches having diameters of 14", 10.7", 8.5, 6.5" and5.2 for carrying out the first draw, four redraws and an ironingoperation, all performed within approximately seven seconds during a 91"continuous uninterrupted down stroke of the press.

The drawing dies carried in the fixed plate system of the press hadclearance with the punches which followed the principles of theinvention with the radius of the first drawing die being A" and theradii of the following four redrawing dies being FIG. 21 of the drawingdepicts the work blanks as they are run in this particular test, whileFIGS. 22 and 23 indicate the pressure pattern obtained with the toolingand material used in this test.

The material used was Alcoa aluminum alloy 3003-0 (dead soft) in theform of 19" presheared circles of .040 stock. In the ironing operationwhich followed the fourth redraw and took place on the 5.2" diameterpunch, the wall of the can was ironed from a thickness of approximately.040" to a finished wall thickness of .027". The finished can had anoutside diameter of 5.25" and a height of 22".

All cans run during this test were without rupture or splitting, andthey had an excellent finish free from defects of all kinds. On removingthe cans from the press, the tops of the cans were slightly trimmed inan amount required to remove the caring at the upper edge of the can,and the workability at the trimmed line was such that a A diameteroutside bead was provided in the top of the can, as a secondaryoperation, by forming the trimmed top edge through 270 without effectingrupture or cracking of the metal at any point, without annealing.

As taken from the press, the cans were tested to determine thedimensions and mechanical properties. The locations on the cans wherethe dimensions and mechanical properties were determined in making upthe following tabulation appear in the lowermost illustration of FIG.21. Typical tabulation of dimensions and mechanical properties of suchcans follows:

Percent elongation Wall Location on can Tensile Yield in 2" thicknessThe tensile and yield determinations are given in the above inthousandths of pounds per square inch.

Example No. 5

This test was run on a press constructed and operated in accordance withthe invention, the press being one used in regular commercialproduction. The set of five telescoping punches had diameters of 14",10.7", 8.5, 6.5" and 4.5 with the first draw die having a radius of A",the first, second, and third redraw dies each having a radius of and thefourth redraw die having a radius of :43".

The material for this test was the same as in Example No. 4 except thethickness of the stock was .050 and the ironing operation performed onthe 4.5" punch following the fourth redraw operation, reducing the wallof the finished can to .040".

The 23 diameter presheared circles of 3003- aluminum alloy (dead soft)were placed in the press and drawn and ironed in one continuousuninterrupted down stroke of the press to produce finished cans havingdiameters of 4.58" and heights of 38". The total reduction in the fivedraw operation was in excess of 80%. It will be noted that the ratio ofdiameter to height in the cans thus produced was approximately 1 to- 8.Cans produced in this test contained no ruptures or splits of any kindand possessed the same high finish, excellent surface quality andavailable workability set forth in respect to Example No. 4. The speedof the down stroke of the press was approximately 70 feet per minute,and the punch to die clearance followed the principles of the inventionheretofore described.

Example No. 6

This test was conducted under the same conditions as Example No. 4,using the same punches and dies, the only departure residing in thesubstitution of Alcoa aluminum alloy 3003-H19 (full hard) for thealuminum alloy 3003-0 (dead soft). The results obtained in this testwere the same as those set forth in Example No. 4 in respect to lack ofrupture or splitting. If anything, the finish was even better and theworkability, after the removal of the can from the press, withoutannealing, permitted the rolling of the same bead mentioned in ExampleNo. 4 with the same excellent results. These results with full hardmaterial were completely unexpected and are unexplainable when viewed inthe light of existing commercial practices. Upon checking the mechanicalproperties of cans produced under this test from 3003-H19 aluminumalloy, it was found that the bottom of the can, as indicated in FIG. 21,had maintained its full hardness and the wall of the can was above fullhard. A tabulation of the mechanical properties of a typical can run inthis test as determined by the Aluminum Company of America follows:

Yield Tensile Elongation Top:

Across grain 28. 4 30. 4. 0 With grain 29. 7 33. 5 4. 0 Across grain- 7.5 30. 2 4. 0 With grain 30. 0 33. 3 4. 0 Across grain 26. 4 30. t) 4. 0With grain 28. 3 31. 8 4. 0 B ottom:

Across grain 25. 7 29. 5 4. 5 With grain 28. 0 29. 2 4. 5

2.0 Example No. 7

In an attempt to determine the upper limits of the.

improvement in workability of drawn and ironed metallic articlesprocessed in accordance with the invention, the tooling used on thepress in running example No. 5 was modified to permit the use of sheetmaterial of .100" thickness. This was accomplished by using the samepunches as set forth in Example No. 5 and substituting larger dies inthe first draw and following four redraw operations. The ironing die ofExample No. 5 was enlarged to reduce the wall of the article to .60" anda second ironing die was added to reduce the wall of the finishedarticle to .040".

As in the case of Example No. 5, the material being drawn and ironed was3003-0 (dead soft) aluminum alloy, and the diameter of the Work blank inthe fiat sheet was 23". Without removing the work blank from thetelescoping punch assembly and without annealing or resorting to anyother form of conventional means heretofore employed for restoringworkability following work hardening, it was possible to draw and ironthe 23" diameter work blank into a finished can having an insidediameter of 4.5 and an over-all length of 66" without metal rupture orsplitting of any kind. The quality of the finish and lack of surfacedefects was equal to that noted in regard to Example No. 5. The speed ofthe stroke of the press and the radii of the dies were as indicated inExample No. 5.

A can formed as described in the preceding paragraph was cut lengthwiseand Rockwell readings taken on the 30-T Scale with a load of 30kg. usinga ball. Starting 4" from the bottom of the can, readings were taken at4" intervals with the final being taken 2" from the open top of the can.The readings were as follows: 26, 28, 27.5, 27.5, 28.5, 29, 30, 29, 30,28, 28, 29.5, 30, 30, 30 and 31.

Whereas, in Example No. 5 the ratio of diameter to height of the drawnand ironed can was approximately 1 to 8, in Example No. 7 this ratio wasincreased to approximately 1 to 15 without metal rupture or splittingand with the article after being drawn and ironed possessing remainingworkability to a degree clearly indicating that the upper limits ofworkability of the material processed in accordance with the invention,as set forth in Example No. 7, had not been reached.

HYDRAULIC SYSTEM OF THE RAM While it is anticipated that means otherthan fluid pressure may be employed to actuate the ram 150, in thecommercial form of the invention the ram is a direct extension of thepiston 156 located in the cylinder 158, the length of which determinesthe maximum stroke of the ram 150. Preferably, the fluid pressure thatis directed against the piston 156 on the clown stroke of the press isof a pulsating character, whereby the ram 150 and the plates of themoving plate system transfer high frequency fluid impulses to thetelescoping punches throughout the down stroke of the press.

In practice, the fluid pressure for effecting the down" stroke of thepress throughout movement of the ram 150 may be provided by means ofpumps 160 and 162 of the axial piston type, in which one or more axialpistons provide positive displacement of fluid each revolution of thepump. In such pumps, each piston will provide a pressure impulse on eachrotation. Pumps of this kind, such as manufactured by DennisonEngineering Division, when supercharged, as by pump 164, are designed tobe operated in the order of 1800 r.p.m. Usually, such pumps have aplurality of axial pistons, with the ones used on the presses of thepresent invention having seven axial pistons and being capable ofdelivering 5,000 p.s.i. at 50 g.p.m. and 100 g.p.m., respectively. Toanalyze the pressure pattern during the down stroke of the press, shownin FIGS. 22 and 23, a high speed electronic analyzer was used,manufactured by the Aeroquip Corportion of Jackson, Mich, and sold underthe trademark Hydrauliscope. This apparatus translates the output of apressure pickup to vertical deflection on a cathode-ray oscilloscope. Toobtain the pressure pattern of FIGS. 22 and 23, the pressure pickup wassubjected to the fluid pressure acting on the piston 156 of the ram 150.FIG. 23 is a reproduction of the curve traced on the screen of thecathode-ray tube during a complete down stroke of the press when tooledto produce the drawn and ironed article depicted in the sequence ofsteps of FIG. 21 and described under Example No. 4.

Referring to FIG. 22, the down stroke of the press Was completed inseven seconds. The pressure pattern indicates the pressure peak d of thefirst draw to be approximately 1900 pounds per square inch actingagainst the ram 150. The first redraw pressure peak rd indicates asimilar maximum pressure. It will be noted that both of the pressurepeaks of the first draw and the first redraw took place within the firstsecond of operation of the press. This indicates a relatively shallowfirst drawing operation, and this fact is confirmed by referring to FIG.21 wherein the sheet metal strip S is reduced to form the work blank B.Between the pressure peak rd of approximately 1900 pounds per squareinch of the first redraw operation and the pressure peak rd2 ofapproximately 1750 pounds per square inch of the second redrawoperation, a greater time interval is indicated than between thepressure peaks d and rd. This indicates a lengthening of the articlewhich is taking place during the first redraw operation, and this isapparent by referring to the form of the work blank B1 of FIG. 21.

FIG. 22 indicates that the pressure peaks M2 and rd3 of the second andthird redraw operations, respectively, took place at approximately 1750pounds per square inch, while the pressure peak rd4 of the fourth redrawoperation took place at approximately 1400 pounds per square inch. Thetime interval between each of the adjacent maximum pressure peaks of theredrawing operations is shown as progressively increasing, indicatingthe progressive lengthening of the article, bearing in mind that it isdesirable to delay the start of one drawing operation until the previousone has been completed. Also, it is desirable to avoid delaying thefollowing drawing operation once the previous drawing operation has beencompleted, as to do otherwise would of necessity extend the length ofthe press unnecessarily. In FIG. 21 the work blank B has taken the formof B1, B2, B3 and B4 at the conclusion of the first, second, third andfourth redraw operations, respectively.

The ironing operation in the press of the invention is indicated at i inthe pressure pattern of FIG. 22 and takes place at approximately 750pounds per square inch. At the completion of the ironing operation, thepressure drops to approximately 500 ounds per square inch as indicatedat e, with a maximum pressure peak of the entire down cycle of the pressapproximately 2450 pounds per square inch at the time the bottom of thearticle is detailed at the end of the down stroke. The work blank Bfollowing the ironing operation has taken the form B of FIG. 21.

In both FIGS. 22 and 23 between the pressure peaks pressure impulses 166have been indicated. In these figures no attempt has been made to depictthe frequency of these impulses, although the same can be determinedwith electronic analyzer apparatus mentioned above. In tests that havebeen conducted on the presses of the present invention using the pumpsof the type above described, the impulses of a frequency in the order of60 cycles per second or more Were present, and were indicated on thepressure pattern in the form of a band having a width depictingamplitudes covering a pressure range in the order of 200 pounds.

Referring to FIG. 23, it will be understood that this is an enlargementof the upper left hand corner of FIG. 22. The frequency of the pressureimpulses making up the wide band of the traced pressure pattern duringthe sweep of the down stroke of the press is determined by the design ofthe pumps employed in the hydraulic system for actuating the ram and thespeed at which the pumps are driven. These impulses are transferred tothe ram 150 and hence to the plates and punches of the moving platesystem of the press, the transfer of the impulses between adjacentplates being through the hydraulic cushions, as well as through thenested arrangement of the punches.

While it is a theory of the present invention that the high frequencyimpulses imparted to the metal-forming components of the pressconstitute one of many factors contributing to the unexpected resultsflowing from the present invention, acceptable commercial results havenevertheless been obtained during experiments when an accumulator wasattached to the hydraulic system of the ram in a deliberate effort toreduce the magnitude of such impulses.

Those skilled in the art will appreciate that by studying and comparingpressure patterns as depicted in FIG. 22 taken with different materialsbeing run in the press and under different conditions of regulation,that the pressure patterns so obtained and compared will be useful inadjusting and operating the press of the invention in commercial use.

To determine the extent the pressure impulses on the ram 150 weretransferred to the press structure closely associated with the punches,the pressure pickup of the electronic analyzer above mentioned wasshifted to the fluid system of the hydraulic cushions 56 of the plate34. The pressure patterns taken at this location were very similar tothose shown in FIGS. 22 and 23, and the width of the pressure patterntraced clearly indicated the existence of impulses 166 of approximatelythe same frequency and magnitude as those determined when the pickup Waslocated in the hydraulic pressure system of the ram 150.

When the press of the invention was operated without any material beingdrawn or ironed, under conditions of operation otherwise the same asprevailed when the pressure patterns of FIGS. 22 and 23 were obtainedwith material being drawn and ironed in the press, it was found that themaximum pressure peaks traced were only slightly lower. On the average,the maximum pressure peaks of the pressure pattern covering the fullsweep of the down stroke of the press, without material being formed,was less than pounds below the maximum pressure peaks when the materialwas being deformed.

The low load yield of the metal of the work lblank B to the drawing andironing operations, as indicated in the preceding paragraph, is deemedto indicate a softening of the metal by two phenomena having cumulativeeffects and which offer a possible explanation for the unusual resultsflowing from the present invention as manifested, for instance, in theaforesaid Examples 6 and 7.

One phenomenon that may contribute to the apparent low load yield of themetal of the work blank B in the press of the invention relates to theeffect of softening produced by high frequency vibration. Where metalbeing drawn has been subjected to the effects of a macrosonic vibrator,one explanation for the softening effect is that the grain boundariesabsorb sufficient energy through in elastic scattering of ultrasonicwaves that the scattering atoms approach melting temperatures withinmilliseconds with the stress required to cause their mobility beingsuddenly reduced. It is a claim of this invention that the pressureimpulses produced by the pumps supplying the fluid pressure foractuating the ram are functioning in a comparable manner.

The other phenomenon, also deemed to contribuite to the low stressyielding of the metal to deformation, pertains to the step of carryingout the deformation of the metal of the work blank B during a single,continuous and uninterrupted rapid stroke of the press withoutappreciable dissipation of the internally generated heat between theacts of deformation.

It appears that the advantages of combining high frequency pulsation ofthe tooling of a deep-drawing press with sequential deformation of themetal taking place in one rapid, continuous uninterrupted stroke of thepress has not been heretofore contemplated, or the improvementsresulting therefrom anticipated.

Always, it should be understood, as heretofore mentioned in regard tomany of the departures of the present invention over previous processesand apparatus, that many factors contribute to the improvements flowingfrom the invention. For example, it has been established that thepiloting of the work blank B from one punch to the other during theredraw operations is extremely important particularly in regard to theforming of high-strength alloys. To give full recognition to this fact,the reduction taking place in the first draw die is preferably less thanheretofore considered good practice. This departure from standardpractice has been taken in order to increase the amount of reductionsthat take place following the first drawing operation during the redrawoperations, at which time the work blank is transferred from one punchto the next.

In the operation of the particular press of the invention on which thepressure patterns of FIGS. 22 and 23 were taken, a 400 horsepowerelectric motor Was used to drive two axial piston-type pumps havingcapacities of 50 and 100 g.p.m. at 5,000 psi. at 1750 r.p.m. The fluidpressure thus provided was directed into a cylinder having a 6" ID andagainst the piston directly connected to the ram of the press.

By substituting a gear pump of 150 g.p.m., but of lower pressurecapacity, for the pumps mentioned in the preceding paragraph, the costof the hydraulic pressure system of the ram may be materially reduced.However, in making this substitution, some of the benefits of the highfrequency vibrations of the fluid pressure system produced by axialpiston pumps may be sacrificed. In such event, the use of transducermeans for effecting vibrations, acting directly on either or both of thehydraulic systems of the press, is anticipated to effect a low loadyield of the work blank B to deformation in the press. For example,hydraulic vibrators of the type presently used commercially to test thefatigue of materials may be coupled with the press to impart vibrationsas high as 500 cycles per second as compared with the pressure impulsesin the order of 200 cycles per second that are obtainable with one ormore axial piston-type pumps having seven pistons and operating at 1750rpm. Such a pump is described in US. Pat. 2,608,158.

For a more detailed explanation of the eflects of macrosound upon metal,reference may be had to an article entitled, Ultrasonic; An Aid to MetalForming? appearing in the April 1964, issue of Metal Process, page 97,published by the American Association of Metals, Mt. Morris, Ill. Thisarticle deals with the effect of high frequency vibration in producingin metal a low load yield to deformation without affecting suchmechanical properties as ductility. Thus, the results of the presentinvention are not anticipated.

HYDRAULIC SYSTEM OF MOVING PLATES It will be observed from a study ofFIGS. 5, 6 and 7 that the locations of the passages 136 do not follow adefinite pattern but are dependent to a great extent on the location oftransverse clearance holes in the plates 30, 32 and 34. As a result, itmay be necessary in practice to drill two or more intersecting holes inthe plates and then plug the ends of some of such holes in order toprovide a connecting fluid passage 136 between one edge of the plate anda passage 148 of a hydraulic cushion. Also, it is not always possible tohave all of the passages 136 exit from the same edge in plates 30, 32and 34. In FIG. this has been possible, while in FIGS. 6 and 7 twooutside connections 168 are shown carried on the vertical edges of plate32 and connecting the passage 136 between the two lower hydrauliccushions and the manifold 138 at the upper edge of the plate.

The manifold 138 of the valve 140 and its associated valve body 170carried on each of the plates 30, 32 and 34 may correspond in generalconstruction and function to that disclosed in US. Pat. 2,938,718,issued to F. M. Williamson. As there is no switching valve associatedwith the plate 34, the valve 149 on that plate may correspondsubstantially to that shown in U.S. Pat. 2,938,- 718. However, on plates30 and 32, which both carry a switching valve 142, the valve 140 is soadjusted'as to operate under the control of the switch valve 142. Suchan arrangement is diagrammatically shown in FIG. 19.

Referring to FIG. 19, the manifold 138 on top of the plate 32 connectswith the passage 136, which in turn extends to and communicates with thepassage 148 of the hydraulic cushions associated with the plate 32. Thevalve body 170 of the valve 140 is mounted on the manifold 138, and hasa bore 172 which aligns with the port 174 in the manifold 138 incommunication with the passage 136. A sleeve 176 is disposed in the bore172 and it is provided with teardrop-shaped ports 1'78 opening into anannular passage 180, which in turn communicates with the passage 182connected to the hydraulic fluid supply 132 through the flexible lines134. An unloading valve 184 is disposed in the sleeve 176 with a spring186 being provided to hold it to its seat in a position closing theports 178. The small port 188 in the valve 184 communicates the fiuidpressure of the hydraulic cushions created by the ram of the press tothe switch valve 142 through the port 190 and passage 192.

Switching valve 142 has a spool Valve 194 with a plunger 196 at one endwhich is adapted to engage the adjustable abutment 154 of the adjacentplate 34 to shift the valve 194 to the left against the tension of thespring 196 from the position shown in which the valve 194 is blockingthe passage 192 to lock the fluid in the hydraulic cushions 54 and,thus, prevent approaching movement of the adjacent plates 32 and 34.When the valve 194 is shifted to the left, the passage 192 is broughtinto register with the annular passage 198 and fluid pressure flow takesplace through the port 200 into passage 292 and, hence, to the port 204.The valve 206 operates to close the port 204, with the amount of fluidpressure required to lift the valve 206 from its seat being determinedby the tension of the spring 208.

The knob 144 may be actuated to vary the tension of the spring 208 ofthe switching valve 142. Lifting of the valve 206 from its seat in theport 264 will enable the flow of fluid in passage 136 to raise theunloading valve 184,

opening the ports 178, to return the fluid trapped in the hydrauliccushions 56 to the supply 132 as the cushions start to collapse and theplates 32 and 34 are able to approach each other. Adjustment of thetension on the spring 208 by the knob 144 will determine the resistanceto collapsing being provided by the fluid in the hydraulic cushions 54.When the unloading valve 184 is under the control of a switch valve 142,the valve 210 may be used to trigger the unloading valve 184 underconditions exceeding the regulation of the valve 142 such as overload.In practice, the tension of the spring 212 of the valve will be greaterthan the tension of the spring 208 of the regulating valve 206.

To enable the fluid returning to the supply 132 to be handled rapidlyand with relatively small lines, two passages 182 are preferablyprovided in the valve body for that purpose. It will be understood thatthe fluid pressure supply 132 is under constant pressure as the resultof air pressure applied to the surface. This pressure is suflicient toreturn the fluid to the hydraulic cushions 54 and to maintain the valvemechanism in Working condition. This pressure is in the order of 20-100pounds and returns the fluid past the ball valve 214 to the passage 136leading to the hydraulic cushions 54. This fluid is also directedthrough the passages 216 to react against the spool valve 194 when inthe position shown.

The flexible hose lines 134 are disposed above the press

